30 April 2009: WHO has raised the alert over Swine Flu to Level 5 - only one step short of a full pandemic. Two days ago they announced Level 4 had been reached - the first time since the steps were introduced following Sars in 2003.

Mexico's President Felipe Calderon announcing partial suspension of all non-essential work and services from 1 May to 5 May. He urged people to stay at home with their families during the shutdown.

Swine Flu continues to spread around the world but while the number of suspected cases is rising rapidly, especially in Mexico, the number of cases with formal confirmation remains small. Officially recognised Swine Flu cases are likely to grow fast as serological test results come through on around 2,500 people that have been in hospital so far in Mexico with severe illness which is suspected to be Swine Flu. Response of Swine Flu to antiviral medication seems to be excellent in most cases so long as it is started within the first two days of illness. These are still very early days, but it does look like the Swine Flu virus is much less dangerous to those infected than Sars was in 2003 - which had a death toll of around 10% of those infected.

To put into context: since normal flu kills up to 50,000 a year in the US and 12,500 in a country like the UK, we should not be surprised or particularly alarmed to see significant death toll from a new Swine Flu pandemic should one occurr. The key issue in terms of impact of Swine Flu will be the predominent age of those most affected. Normal flu tends to kill people who are old and frail, whose life expectancy may be limited for many other reasons. But history shows that radically different kinds of flu viruses can strike younger people very hard - probably because of an over-reaction by their own immune systems.

The trouble is that while normal flu deaths attract very little attention, we can see that it is likely that deaths from Swine Flu may each become a mini-headline, creating the impression in the general public of a massive and uncontrollable plague, even if Swine Flu turns out to be less dangerous than a type of normal human flu. And that in turn is likely to lead to many tens of millions of people making their own decisions about protecting themselves and their families from Swine Flu - not travelling, taking children out of school, cancelling public events, not eating in restaurants, working at home and so on.

A key challenge is that it is possible that a large number of mild cases of Swine Flu have been missed in Mexico - confused with ordinary flu. Many parts of normal life in Mexico city remain shut down - schools, restaurants and so on - while Argentina has cancelled flights from Mexico, despite WHO advice that the virus is likely now to have spread so widely that containment by such measures is neither practical nor desirable.

Director General Margaret Chan urged all countries to activate their pandemic plans, including heightened surveillance and infection-control measures. She said action should be undertaken with "increased urgency. It really is the whole of humanity that is under threat in a pandemic." But the world is "better prepared for an influenza pandemic than at any time in history". For the first time, a pandemic can be tracked in real time, necessary because the virus could mutate at any time into a more dangerous strain - or a milder one.

29 April 2009 WHO press release on Swine Flu:

The situation continues to evolve rapidly. As of 18:00 GMT, 29 April 2009, nine countries have officially reported 148 cases of swine influenza A/H1N1 infection. The United States Government has reported 91 laboratory confirmed human cases, with one death. Mexico has reported 26 confirmed human cases of infection including seven deaths.The following countries have reported laboratory confirmed cases with no deaths - Austria (1), Canada (13), Germany (3), Israel (2), New Zealand (3), Spain (4) and the United Kingdom (5).

WHO advises no restriction of regular travel or closure of borders. It is considered prudent for people who are ill to delay international travel and for people developing symptoms following international travel to seek medical attention, in line with guidance from national authorities.There is also no risk of infection from this virus from consumption of well-cooked pork and pork products. Individuals are advised to wash hands thoroughly with soap and water on a regular basis and should seek medical attention if they develop any symptoms of influenza-like illness.

The WHO press release takes no account of suspected cases which are the vast majority of those receiving medical attention right now.

* Dr Patrick Dixon is a physician and a Futurist. He has been heavily involved in fighting the spread of HIV in many of the world's poorest nations, for the last 21 years and advises many large corporations on a wide range of business risks including health-related issues.